Objectives The main symptom of diabetes mellitus (DM) is hyperglycaemia, and patients with DM often have microvascular complications, such as retinopathy, neuropathy, and nephropathy; macrovascular complications, such as coronary heart disease, peripheral arterial disease and cerebrovascular disease; and oral complications, such as xerostomia, hyposalivation and periodontal disease. The main aim of this study was to evaluate the submandibular and parotid glands in type 2 DM patients and healthy individuals and to determine the changes in the salivary glands caused by diabetes. Materials and methods In this study, the salivary glands of 100 patients (50 individuals with type 2 DM and 50 healthy individuals) were evaluated by ultrasonography (US). Echogenicity, parenchymal homogeneity, hypoechogenic and hyperechogenic areas, margin characteristics, and vascularity of the glands were analysed. The anteroposterior, superoinferior, and mediolateral lengths and volumes of the submandibular glands were measured. Results Statistically significant differences in submandibular gland echogenicity, parotid gland vascularity, and hyperechogenic reflections of the parotid glands were observed between the groups (p < 0.05). In addition, the volume and dimensions of the submandibular glands were significantly greater in the type 2 DM group. Conclusions DM leads to changes in the salivary glands. US, which has many advantages for salivary gland imaging, is a highly effective method for investigating these changes in individuals with diabetes. Clinical relevance US, which is well tolerated by patients and does not involve ionizing radiation, can be used for long-term monitoring of the effects of diabetes mellitus on the salivary glands.